How to Draw Cord Blood Gas

In a fetus, the blood is transported from the placenta to the baby via the umbilical cord. Oxygen is picked up by the umbilical vein and transported to the baby. The umbilical artery transports carbon dioxide back to the placenta. A cord blood gas is a test that can measure the amount of oxygen and carbon dioxide in the blood. It can also determine how acidic the blood is. At birth, a doctor may order a cord blood gas drawn to help determine if the baby was deprived of oxygen during labor.

Difficulty:

Moderately Challenging

Instructions

1. Be sure the umbilical cord is clamped on both ends. This will usually be done by the physician at birth. Handle the cord carefully. It's delicate and slippery. If the cord is damaged, it may not be possible to draw a sample from it.

2. Identify the umbilical artery and the umbilical vein. In the cord the vein is the larger of the two. Usually a sample is drawn from the umbilical vein in one syringe and another sample from the umbilical artery in a different syringe. Be sure the syringes contain heparin. This will prevent the blood from clotting. If the blood clots, the sample may not be able to be run through the blood gas machine.

3. Grasp one end of the umbilical cord with your non-dominant hand to prevent it from moving. With the dominant hand, hold the syringe between the thumb, the index finger and the middle finger, similar to how you would hold a pencil.

4. Insert the needle into the umbilical vein slowly at a 45-degree angle. Be careful to avoid going completely through the vein. Pull back slowly on the syringe to allow it to fill with blood. Obtain the required amount of blood according to hospital policy and remove the needle from the umbilical cord.

5. Remove the needle from the syringe and push any air bubbles out of the syringe. Bubbles can interfere with accurate results if they are left in the sample. Place a cap on the syringe to prevent the blood from spilling out. Label the syringe according to hospital polices. Be sure to indicate on the label the sample is from the umbilical vein. Repeat the same procedure in step four on the umbilical artery and label the sample accordingly.

Tips & Warnings

• Always take the cord blood gas sample to the lab for analysis promptly. Allowing the sample to sit around too long can cause inaccurate results. Keep personal safety in mind. Always use gloves when drawing a blood sample. Since the blood may also squirt when you insert the needle, consider using a face shield.

• Do not discard the umbilical cord. Ask the labor and delivery nurse where the cord should be placed after the blood sample is drawn.